The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert addressees to the need to follow the manufacturer's instructions regarding proper operational checks of alarm ratemeters. It is expected that recipients will review this information for applicability to their facilities and consider actions, as appropriate, to avoid similar problems. However, suggestions contained in this information notice are not new NRC requirements; therefore, no specific action nor written response is required.

Description of Circumstances:

Two radiographers were working under reciprocity in an Agreement State, and both donned film badges, direct-reading dosimeters (DRDs), and alarm ratemeters. At the start of the shift, the radiographers checked the operation of their NDS Products (NDS) Model RA-500 alarm ratemeters by pushing their buttons and hearing audible signals. After an exposure,
the crew became distracted and failed to read their survey instruments when approaching the exposure area to prepare for the next shot. After set-up of the next shot, the crew returned to the camera and attempted to expose the source. The crew realized that the source was already exposed, so they retracted the source. The crew checked their DRDs and saw that they were off-scale. Neither alarm ratemeter alarmed during the event.

The Radiation Safety Officer (RSO) performed an operational check of the licensee's entire inventory of alarm ratemeters soon after the event by pushing a button and hearing an audible signal. The RSO then tested the response of all its alarm ratemeters by exposing them to radiation inside of a permanent radiographic installation. The RSO noted that the two alarm ratemeters that were used during the event plus an additional one failed to alarm when tested in a radiation field in excess of 5 mSv/hr (500 mR/hr) even though the operational checks "passed". The RSO sent the three alarm ratemeters back to NDS for repair. NDS reported that all three alarm ratemeters had dead or weak batteries.

Based on film badge results and licensee dose calculations, one radiographer received approximately 25 mSv (2.5 rem) from the event. The other radiographer received less than 3 mSv (300 mrem).

NRC learned that NDS' operation manual for the Model RA-500 states that the battery and audio tone check requires pressing a button after the unit is powered on. The red LED lights up (visual signal) if the battery is O.K. and the alarm will sound (audible signal). If either the visual or audible signal fails, the alarm ratemeter must not be used. An NDS representative confirmed that the audible signal is only a speaker test. The battery check (i.e., voltage across the detector) requires the visual signal. Therefore, failure to check the LED light equates to failure to check the battery.

The licensee's operating procedures and instructions to personnel did not include both operational checks, and this rendered the battery check inadequate. The licensee's failure to perform adequate operational checks appeared to explain why alarm ratemeters failed during the event. Had the alarm ratemeters been properly checked, the weakened state of the batteries could have been detected. The batteries would have been replaced and the alarm ratemeters would have alarmed and alerted the radiographers to an exposed source, so they could have taken actions to reduce their radiation exposures.

Discussion:

Licensees are reminded of the need to review and incorporate device manufacturers' recommended procedures in developing operating procedures, particularly those regarding operational checks of alarm ratemeters. NRC expects licensees to use safety-related equipment in accordance with the manufacturer's instructions for operation and maintenance.
Licensees should emphasize to workers, especially in industrial radiography activities, the need to strictly follow such procedures.

This information notice requires no specific action nor written response. If you have any questions about the information in this notice, please contact the technical contact listed below or the appropriate NRC regional office.